Castor - Java highly nested XML problem [Spring]

[this is a cross-post from the castor maillist-got no response there yet]

I got castor to working [unmarshalling] with an "unnested" xml file, but when I nest the elements, it gives me an :error:
of: "Ignoring XXYY no descriptor was found" for anything under the main element "Build".
Here's the "simple" xml:

it seems to find everything, but has a problem with "descriptors"... here's the TRACE output:

I've tried an amazing amount of variations on "location," including leaving it out and still, it doesn't map: